Which statement about Mode 1 SIF coding is true?

Which statement about Mode 1 SIF coding is true?

• A. It provides encryption of transponder replies
• B. It uses 64 codes
• C. It allows up to 32 codes
• D. It is the only mode used for simplicity

Answer: (C)

Mode 1 SIF coding is about how many distinct identification codes can be conveyed in the SIF reply. It uses a five‑bit code field, which yields 2^5 = 32 possible values. So up to 32 unique codes can be assigned for identification purposes. This is not encryption—the codes are transmitted as plain identification values, not as encrypted data. It also isn’t 64 codes (that would require six bits). And there are other SIF modes used for different purposes, so Mode 1 isn’t the only mode or specifically chosen for simplicity.

Mode 1 SIF coding is about how many distinct identification codes can be conveyed in the SIF reply. It uses a five‑bit code field, which yields 2^5 = 32 possible values. So up to 32 unique codes can be assigned for identification purposes. This is not encryption—the codes are transmitted as plain identification values, not as encrypted data. It also isn’t 64 codes (that would require six bits). And there are other SIF modes used for different purposes, so Mode 1 isn’t the only mode or specifically chosen for simplicity.